Plasma arc torches are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. The plasma arc torch is typically connected to a power supply that provides both gas and electric power for operation of the plasma arc torch and is operable through a trigger disposed within a torch handle for activation of the gas and the electric power. Because the plasma arc torch creates intense localized heating at relatively high plasma exit velocities, inadvertent operation of the trigger could result in a risk of personal injury and/or damage to surrounding objects.
To reduce the risk of inadvertent torch ignition, control systems and devices are commonly provided in plasma arc torches of the known art. For example, control systems are provided within some known art power supplies, which are often at a remote location relative to the operator, to initiate or terminate gas flow to the plasma arc torch. However, such control systems require the operator to either look away from the torch or the workpiece where an operation is being performed or delay operations in order to manipulate the gas flow. Accordingly, the use of gas control systems within the power supply is somewhat inefficient and increases the risk of inadvertent torch operation. In addition to control systems, control circuits are also known that isolate current flow to the torch until gas flow is initiated. Further, audible warnings are provided in some known systems to notify the operator that the torch is ready for operation so that the torch is not improperly used.
Additionally, activation of gas flow only, i.e. no electric power, is often advantageous in certain applications such as for cooling torch components, (e.g., electrode, tip), or the workpiece. However, many plasma arc devices do not provide for a gas only mode of operation, and those that do provide for such a mode require the operator to initiate and terminate the gas flow at the power supply, not local to the plasma arc torch where operations are being performed. As a result, operation of a gas only mode is relatively time consuming and cumbersome in plasma arc torch systems of the known art.
Inadvertent torch operation may also occur when the trigger is prematurely depressed by the operator while the torch is being positioned for operation. The trigger may also be inadvertently depressed when the torch is being disassembled for maintenance or when being placed down onto a surface or object that causes the trigger to be depressed. Accordingly, devices have been provided with plasma arc torch triggers of the known art to reduce the risk of inadvertent torch operation through engagement of the trigger. One known trigger system provides a safety member to prevent inadvertent operation of the torch, wherein the operator must reposition the safety member in order to depress the trigger. Unfortunately, engagement of the safety member requires increased manual dexterity of the operator (generally wearing gloves) to engage the trigger for operation of the plasma arc torch, which is often cumbersome and time consuming when the plasma arc torch is continually being ignited and turned off
Accordingly, a need remains in the art for a device and method that provides gas control local to the torch and operator, and which provides for multiple operating modes to control the gas flow separate from the electric power. A further need exists for a device and method that reduces the risk of inadvertent torch operation and that requires less manual dexterity than trigger systems of the known art.